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The German anti-doping agency said earlier that 30 athletes were being investigated in connection with a possible doping affair involving a doctor in the city of Erfurt.

NADA said they were looking into each of the 30 cases where the doctor, once part of the Olympic base in Erfurt, was suspected of having used a blood infusion system after exposing the blood to ultra-violet rays.

On Sunday, the German TV channel ARD named Kittel as one of the athletes involved.

His 1t4i team, however, said Kittel was blameless, saying he met the doctor, named by the Erfurt prosecutor's office as Andreas Franke, as had many athletes involved with a German Olympic support group.

"As an 18-year-old sportsman from the region of Erfort and therefore part of this Olympic point of support, Marcel Kittel should contact the doctor concerned in case of illness," the team said in a statement.

"In 2007 and 2008, Marcel visited this doctor when he was ill. The doctor decided to treat him with the UV-treatment mentioned in the program of Sportschau (on ARD)."

1t4i added that Kittel, as well as team mate Patrick Gretsch, had not received the UV treatment since well before 2011, when, they say, "the World Anti-Doping Agency changed the anti-doping codes and all treatments with blood were prohibited".

The team explained that Franke would take "a very small amount (a few cc) of blood from the body via a syringe and put this under UV lighting immediately to fight the infection in the blood.

"This blood was subsequently reinserted into the body. The entire treatment did not take more than a few minutes. It did not involve an infusion or transfusion."